Vista - ImageBrush Tiling

I hope this isn't a bug. I am setting the background of a <Grid> to a
JPG image using:

<Grid.Background >
<ImageBrush ImageSource="stars.jpg" TileMode="Tile"/>
</Grid.Background>

The problem is that when I maximize my window (which triggers a resize
of my grid), the grid doesn't tile the background when the window
exceeds the image size... the grid stretches my image.

When I use "TileMode="Tile" and "Stretch="None", I actually get no
background.

When I set TileMode to "None" - it actually gives me the _SAME_ results
as when I use TileMode = "Tile".

Any thoughts?

I had tried this particular tactic multiple times. I'm not in the habit
of posting to this newsgroup without first reading the documentation.
What I didn't do was the ViewportUnits="Absolute" ... All other
attempts to specify the viewport produced the same obscure stretching
results.

Adding ViewpotUnits=Absolute to the mixture did the trick.. Now I just
need to figure out how to make my bitmap tile without a seam